Combined radio transmitter and loud-speaker installation



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COMBINED RADIO TRANSMITTER AND LOUDSPEAKER INSTALLATION Filed Feb. 8'. 1945 per iiil

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Mukhi n Patented Dec. 30, 1947 COMBINED RAlIEBIO TRANSMITTER AND `LOUD-SPEAKER INSTALLATION .Cuthbert George` Garland Withey, London, .Eng-,- land, assignorto International Marine .Radio Company Limited, London,1 England, a` British Company fApplicationFebruary 8, 1945, Serial No. 5765838 rIn Great Britain February 21,1944

`2 Claims. z1

This invention vconsists .in a. combined? radio transmitter and loudspeaker.installation, more particularly rthough not exclusively for use aboardv ship. Ships are usually tted with radio apparatusand also frequently are. providedwith a loudspeaker installation. It is the object of this invention to effect economy inthe apparatus provided for these separate-purposes.

. According to the presentfinventionfweprovdc the combination with ara'dio:transmitterinstallation of a loudspeaker. installatioma microphone additional to that of the radio transmitter installation, a-switchto connectthe said microphone to the input ofthe radio transmitter anda second switch adaptedto connect'the outputof a low frequency amplifier inrsaid. radio transmitter installation either to the radio frequency-'stages of said last mentioned installation orto theloudspeaker installation.

The invention 'will befbetter understood from the following description taken .in conjunction with the accompanying drawings in which:

Fig. 1 is a typical circuit diagram of an installation according to the invention in a casein which the radio transmitter uses. plate circuit modulation of suitable power to load the loudspeaker.

Fig. 2 is a schematic diagram: of an installation according to the invention in a case in which the radio transmitter uses grid circuit modulation of insufficient power fully to load the loudspeaker.

Referring to the drawings, Fig. 1 is a circuit diagram of an installation comprising a radio transmitter installation of. a Well known kind combined with a loudspeaker installation in accordance with this invention. The output from a high frequency oscillator O is connected by means of a transformer T3 in push pull to the grids of two valves Vl and V2, the anodes of which valves are in parallel and are connected to the high tension supply through a tuned circuit and the secondary of an audio frequency transformer T2. The microphone, key buzzer audio oscillator or other sources of signals is connected tothe points MI, M2 and thus to the primary of a transformer TI, the secondary of which is connected to the input of a push pull audio frequency amplifier V3, V4, the output of which is connected to the primary of transformer T2. The inductance of the tuned high frequency output circuit serves as the primary of transformer T4 the secondary of which is included in the antenna circuit. According to the invention a switch SI is provided, which in one position connects the secondary of transformer T2 in its normal position in the an- 2 ode circuit of valvesV Viand V2-so that thahigh frequency is modulated from the` signal source and in another position connects the"secondary oftransformer T2 toav directional loudspeaker LS. The lat-ter may .include an impedance matching transformer ifnecessary.

It will be noted that'..the connections vmade Ahy the switch 'Si are such that 'whent'he -audio frequency amplifier V3, V4. isconnected-to the loudspeaker LS the high tensionisupplyis.disconnected from the valves yVl. and V2. andthe oscil lator O so that the H. F. portion ofthe installation isrendered nonradiating, butremainsaconnected to the valves V3 vand V4.

Since itis'usually required thatthe directions or informationjgiven vover the loudspeaker-.LS should originate from thevbridge, airnicrophone K with a push button: S2 switch. in Aseries there with is situated .on the" bridge andzvconnecteditc the wiresMS in shunt tol the normal microphone etc..of the radio transmitter.

InFig. 1 ano-de vmoclulationis usedandthe modulation. in the radio transmitterztakesplace at a high power stage. In such circuits the audio frequency amplifier V3, V4 is usually of sufficiently highpower to. develop -a volume of sound-inw. directional .loudspeaker LS adequate for lhailing over thev maxim-um distances at present/used for such purpose.

Fig. 2 is one example of the application of the invention to an installation in which the radio transmitter uses grid circuit modulation and the audio frequency output is low (below 10 watts). The input to a high frequency amplifier HFA includes in series secondaries of high and audio frequency transformers by `means of which the outputs of a high frequency oscillator O and an audio frequency amplier LFAI are impressed thereon.

The signal source is connected to points MlF M2 in the input of amplifier LFAI. In applying the present invention, a switch SI is provided and in one position completes the connection between the secondaries of the high and audio frequency transformers in the input of amplifier HFA and in the other position connects the secondary of the audio frequency transformer to the input of a second audio frequency amplifier LFAZ the output of which is connected to a directional loudspeaker LS. The second audio frequency amplifier LFAZ is necessary because in the case of a low power radio transmitter such as is illustrated, the low frequency amplifier LFAI does not usual-` 1y develop sucient power for hailing over the maximum distances for which a directional loudspeaker is at present used. Even in this case, however, considerable economy in components over separate radio transmitter and loudspeaker installations is eiected. In the same way as described with reference to Fig. 1 a microphone with a push button switch located in the bridge is connected across the points Ml, M2 in shunt to the normal microphone of the radio transmitter installation.

The loudspeakers may be used for aural communication (alternative to radio) between ships in convoy, between the bridge or other control centre of a ship and remote sections of the same ship, between a ship and a lighthouse or other point on shore, e. g., for docking instructions or the like, or it may be used between a ship and lifeboats or other rescue services.

The installation of a loudspeaker system to utilise part of the equipment of the audio transmitter possesses considerable advantages over a separately installed loudspeaker system in that separate microphones, ampliers, batteries, or generators are not in general required; conversion of any ship tted with a radio transmitter is easy; the changeover from radio to loudspeaker communication can be instantaneous, e. g., as distance increases and aural communication fails via the loudspeaker channel, contact can almost instantly be made by radio, whilst the possibility of using Morse communication via the loudspeaker allows greater range to be obtained by direct aural transmission.

What is claimed is:

1. In a communication system for a ship where lt is desirable to communicate with another ship by a, loudspeaker or by radio `using either voice or code signals, the combination of, aradio transmitter having a radio-frequency circuit portion and an audio-frequency circuit portion, a microphone connected to the input of the audio-frequency circuit portion, means to introduce code signals to the input of the audio-frequency circuit portion, a loudspeaker operable when connected to the output of the audio-frequency circuit portion to reproduce the voice or code signals for acoustic transmission to another ship, and a switching assembly adapted to connect the output of the audio-frequency circuit portion selectively to the loudspeaker or to the radio-frequency cir- 4 cult portion whereby the voice or code signals are transmitted by the loudspeaker acoustically or by the radio transmitter, said switching assembly including a switch unit which is closed by the connecting of the audio-frequency circuit portion to the radio-frequency circuit portion and which switch unit when' closed connects a source of power to energize the radio-frequency circuit portion.

2. In a communication system for a ship where it is desirable to communicate with another ship by a loudspeaker or by radio using either voice or code signals, the combination of, a radio transf mitter having a radio-frequency circuit portion of the plate-circuit modulation type and an audiofrequency circuit portion which includes an audio-frequency transformer, a microphone connected to the input of the audio-frequency circuit portion, means through which code signals may be introduced to the input of the audio-frequency circuit portion, a loudspeaker operable when connected to the output of the audio-frequency circuit portion to reproduce the voice or code signals for acoustic transmission to another ship, and a switching assembly adapted to connect the secondary winding of the audio-frequency transformer selectively to said loudspeaker or in series with the plate circuit of said radio-frequency circuit portion whereby the voice or code signals are transmitted by the loudspeaker or by the radio transmitter, said switching assembly including a switch unit which is closed by the connecting of the audio-frequency circuit portion to the radiofrequency circuit portion and which switch unit when closed connects a, source of power to energize said radio-frequency circuit portion through the secondary winding of said audio-frequency transformer.

CUTI-IBERT GEORGE GARLAND WITHEY.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,138,598 Goldsmith Nov. 29, 1938 2,139,006 Durst Dec. 6, 1938 

